The MTDC Portable Vehicle Washer
Sump Pumps and Settling Tanks

An electrically powered sump pump moves wash water collected on the mat into two 175-gallon, cone-bottom settling tanks (figure 10). The water flow enters the first settling tank through large PVC pipes near the bottom of the tanks. The water flow enters near the bottom to minimize flow velocities and turbulence, increasing the likelihood that particulate will settle in the tanks.

Figure 10—Two cone-bottomed tanks (background)
are used as settling tanks to remove the larger
particulate. Used wash water from the mat
flows to these tanks before it is filtered.

A 2-inch connector near the top of each tank allows over-flow water from the first settling tank to flow into the next settling tank. Water enters the second settling tank near the bottom of the tank through PVC pipe attached to the overflow connector between the two tanks.

The overflow from the second settling tank flows into a smaller open-barrel tank (figure 11). A filter housing with a large-mesh filter (800 microns) is attached to the overflow pipe, trapping debris such as needles or leaves and most large seeds. Another sump pump in this open tank moves the water through two filters and back to the main 550-gallon holding tank.

Figure 11—Overflow from the settling tanks flows to the
overflow tank (left). A sump pump inside the overflow
tank pumps water through two filter housings to the
holding tank. The filter housings use polypropylene
or polyester felt and nylon monofilament filters to
remove particulate of different sizes, depending
on the user's requirements. The size of particulate
filtered can range from 800 microns to as
fine as 3 microns.

Ball valves and hoses attached to the bottom of each of the settling tanks allow them to be drained.

Filter Housings and Filters

The wash water is pumped through two filter housings and back to the main holding tank. Each filter housing uses felt filter bags rated at sizes ranging from 800 microns down to 3 microns to remove particulate matter or seeds larger than the bag's rating. Any combination of bags can be used, depending on the size of seeds or spores that are targeted. A 100-micron filter bag should catch all seeds, while bags with smaller mesh sizes could be used to trap spores.

Each housing is equipped with pressure gauges to determine when the filters are clogging. A pressure of 15 to 20 pounds per square inch indicates that the filters are nearly full. The filters can be stored for analysis or backwashed to remove all the debris and reused.

Electrical Power

A 5,000-watt gasoline generator (figure 12) provides electrical power to operate the two sump pumps. The generator can also be used to power lights and any other electrical accessories.

Figure 12—A 5,000-watt gasoline generator supplies power for
the two sump pumps and can provide power for other
electrical needs.

Mat Reel

A manually operated reel has been fabricated to help set up, transport, and store the mat (figure 13). The reel is designed so that the mat can be unrolled easily when the washing station is being set up. An operator holds one end of the mat down, releases the reel's locking mechanism, and pulls the trailer forward over the mat's felt underlayment. Once the mat is in place, it can be unfolded for use.

Figure 13—The mat reel is used to roll up the mat for transportation
and storage.

Before storage, the mat should be thoroughly washed to remove any rocks and debris, dried as thoroughly as possible, and folded to a width of 46 inches. The front end of the mat can be lifted, locked into the reel, and reeled in. A locking mechanism (figure 14) prevents the reel from unwinding. Tiedowns and straps hold the mat in place.

Figure 14—The mat reel's locking mechanism
prevents the mat from unrolling accidentally.